This invention lies in the field of gas-liquid separation.
More particularly, this invention lies in the field of gas-liquid separation of fluids, which are emergency relieved products, which are passed to a flare for complete smokeless combustion before release to the atmosphere.
Flares for emergency relieved products are designed for and operate properly only when the products flared are in gaseous phase. Since, from the point of relief, the products may be partially in liquid phase, and thus unsuited for discharge from the flare, it is necessary for the relieved products to pass through gas-liquid separation before reaching the flare, for discharge of gaseous phase products for flare burning within the atmosphere.
Typically, and for gas-liquid separation, flare systems include a "knock-out pot" which is simply a vessel of considerably larger cross-sectional area than that of the line or conduit to the flare, through which the fluid is being passed. Such a knock-out pot is generally, in length, some 5 to 20 times the diameter of the conduit. While these knock-out pots remove a large portion of the liquid because of the decreased flow velocity and permit the continued passage of the gases to the flare, they do not remove all of the potentially recoverable liquid, dependent, of course, on the distribution of drop sizes.
This is because some of the liquid carried by the gas stream is in the form of droplets of 0.015 inch diameter and greater.
In the knock-out drum, the gas velocity is as low as 9 fps, which is the average knock-out drum gas movement velocity. At this velocity, the gas will carry the 0.015 inch diameter droplets right on through the knock-out drum to the flare. Drops of this size carried with the gas result in a significant loss of product liquid. Also, they provide a problem in burning the mixture with complete smoke suppression, as is required in flares. The liquid is in most cases valuable hydrocarbons, and their loss is an unwarranted energy loss.
In the prior art, it has been common to use the knock-out pot as a means of separating large liquid droplets with partial removal of the liquid by this means.
In the prior art, it has also been common to use centrifugal separation to remove a large part of the larger drops entrained in a gas flow.
It has also been common in the prior art to use demisters. In such devices, the flow of fluid causes the liquid droplets to impinge on the surface of the elements of the demister and to attach themselves to the surface and to flow down by gravity to be collected at the bottom of the vessel.
It is, therefore, a primary object of this invention to provide in one simple mechanical system, four stages of separation which involve the principles of centrifugal separation, baffle diversion separation, low transit velocity separation, and demister separation, with novel combination of the four methods, and an improved construction of the demister separation elements.